The effects of 1-beta-D-arabinosylcytosine (ara-C) given for 5 days on body weight, on the weights of the prostate, seminal vesicles and testis, and on the polyamine content (putrescine, put; spermidine, spd; spermine, spm) in these organs were examined in rats. The body weights of the ara-C-treated rats showed a decrease of 13% (P less than 0.01) and the weights of the prostate, seminal vesicles and testis were reduced by 20% (P less than 0.05), 13% and 5.0% (P less than 0.1), respectively. However, put, spd and spm contents in the ara-C-treated prostate were increased 1.2, 1.8 and 2.9 times, respectively. The contents of these polyamines in the ara-C-treated seminal vesicles increased about 40% for all polyamines. Both spd and spm in the treated testis showed a significant increase of about 20% (P less than 0.05) as compared with the control. In addition, the total polyamines in the whole organs increased significantly in both the prostate and testis.